The present invention relates to a refrigerator; and, more particularly, to a direct cooling type refrigerator.
Generally, a refrigerator is an apparatus for storing various foodstuffs in either a frozen or a refrigerated condition to extend the freshness of the foodstuffs for a long time. Such a refrigerator essentially includes a compressor, a condenser, and an evaporator. The compressor circulates a refrigerant by compressing the refrigerant. The condenser serves to condense the refrigerant into a liquid phase, and the evaporator serves to generate a chilled air by evaporating the liquid phase refrigerant.
The refrigerator further includes a freezing chamber and/or a refrigerating chamber. The freezing chamber is alternatively referred to as a freezing compartment and serves to store frozen foods such as meats or an ice cream. The refrigerating chamber is alternatively referred to as a refrigerating compartment and serves to store foods at a lower temperature than a room temperature.
There have been developed various types of refrigerators to satisfy various needs, and a direct cooling type refrigerator is one of them. The direct cooling type refrigerator is alternatively referred to as a natural circulation type in which the chilled air naturally circulates in the freezing or the refrigerating chamber because of a temperature difference therebetween. The evaporator of the direct cooling type refrigerator usually directly contacts an inner case forming the freezing chamber and/or the refrigerating chamber.
With reference to FIGS. 1 and 2, a conventional direct cooling type refrigerator 1 and problems thereof will be explained. FIG. 1 shows a top plan view of the conventional direct cooling type refrigerator 1 while FIG. 2 shows a cross-sectional view taken along a line IIxe2x80x94II of FIG. 1.
In FIG. 1, the direct cooling type refrigerator 1 includes a cabinet 2, a door 50 assembled with the cabinet 2, an inner liner 4 inside the cabinet 2, and a freezing chamber and/or a refrigerating chamber 60 defined by the inner liner 4. The inner liner 4 is alternatively referred to as an inner case. An evaporator (not shown), a condenser (not shown), and a compressor (not shown) are also contained in the direct cooling type refrigerator 1. The door 50 and the cabinet 2 are assembled usually with, e.g., hinges (not. shown), such that the door 50 can open or close the freezing chamber and/or the refrigerating chamber 60. If both the refrigerating chamber and the freezing chamber 60 are contained in the direct cooling type refrigerator 1, the refrigerating chamber is usually disposed under the freezing chamber 60.
As shown in FIG. 2, the conventional direct cooling type refrigerator 1 further includes a refrigerant pipe 10 and an insulator 20. The refrigerant pipe 10 is disposed on the inner liner 4 and serves as the evaporator. The insulator 20 is interposed between the inner liner 4 and the cabinet 2 to insulate the freezing or the refrigerating chamber 60. The insulator 20 is usually polyurethane, and the inner liner 4 is usually polystyrene. The inner liner 4 conventionally has a multiplicity of recesses 4a where the refrigerant pipe 10 is embedded to contact the inner liner 4. The refrigerant pipe 10 is interposed between the inner liner 4 and the insulator 20. The refrigerant is evaporated inside the refrigerant pipe 10, thereby reducing the temperature of the freezing chamber 60.
The conventional direct cooling type refrigerator 1 presents quite a few problems, e.g. a large temperature variation along the inner liner 4. Because the refrigerant pipe 10 directly contacts the inner liner 4 only at the plurality of recesses 4a and the inner liner 4 is conventionally made of a heat-resistive material, temperature rapidly differs between a pipe-contacting portion and a non-pipe-contacting portion of the inner liner 4. The above-mentioned temperature variation causes a low cooling efficiency of the conventional direct cooling type refrigerator 1.
Another problem arises in that the inner liner 4 is produced by applying a technology of thermoforming a thermoplastic sheet. Such a technology presents quite a few drawbacks, e.g. difficulties in the dimensional control of the sheets. That is to say, the size, shape, depth, or position of the recesses 4a is difficult to be uniform throughout the overall inner liner 4. If portions of the recesses 4a are irregularly formed, an assembly of the refrigerant pipe 10 and the inner liner 4 is difficult and therefore a point contact may exist therebetween. The above-mentioned point contact causes an irregular temperature variation along a longitudinal direction of the recesses 4a. 
Further, when the point contact exists between the refrigerant pipe 10 and inner liner 4, a portion of the insulator 20 may penetrate into gaps formed therebetween because of the point contact. The penetrated portion of the insulator 20 prevents heat transfer between the refrigerant pipe 10 and the inner liner 4, thereby deteriorating the cooling efficiency of the conventional direct cooling type refrigerator 1.
On the other hand, because the refrigerant pipe 10 is very lengthy and the inner liner 4 is heat-resistive, a latent temperature variation exists along the refrigerant pipe 10.
It is, therefore, an object of the present invention to provide a refrigerator having a relatively lower temperature variation so as to present a high cooling efficiency. According to a preferred embodiment of the present invention, there is provided a direct cooling type refrigerator including: an outer case; an inner case inside the outer case; a metal plate disposed on the inner case; an evaporator disposed on the metal plate; an insulator filling gaps between the inner case and the outer case; a first bonding means for attaching the metal plate on the inner case; and a second bonding means for joining the evaporator with the metal plate.